sound waves

Sound

A form of energy that spreads out through space.

Pitch

Subjective impression about the frequency of sound; high pitch indicates high frequency.

Infrasonic

Sound waves with frequencies below 20 hertz.

Ultrasonic

Sound waves with frequencies above 20,000 hertz.

Compression

The pulse of compressed air created as sound travels through a medium.

Rarefaction

The pulse of low-pressure air created as sound travels through a medium.

Medium

The material through which sound travels (solids, liquids, gases).

Elasticity

The ability of a material to change shape in response to an applied force and then return to its original shape.

Decibel (dB)

Unit of intensity for sound, measuring sound intensity.

Natural Frequency

The frequency at which an object vibrates when disturbed.

Forced Vibration

Occurs when an object is made to vibrate by another nearby vibrating object.

Resonance

When a vibrating object is matched by an external force at its natural frequency, increasing its amplitude.

Constructive Interference

Occurs when the crests of one sound wave overlap the crests of another, resulting in louder sound.

Destructive Interference

Occurs when the crest of one wave overlaps the trough of another, resulting in reduced sound intensity.

Speed of Sound

Varies in different media; faster in solids than in liquids or gases and cannot travel in a vacuum.

Threshold of Hearing

The minimal level of sound intensity at which an average human can hear.